KABUL (Reuters) - Hospitals and clinics in Afghanistan have increasingly been targeted by armed groups over the past two years, weakening an already degraded health system, a children's rights group said in a report issued on Monday.

Watchlist on Children and Armed Conflict said attacks had further restricted or even blocked medical care in a country where almost a third of the population of more than 30 million lacks access to basic health services.

The report, based on interviews in the provinces of Helmand, Kunduz, Nangarhar and Maidan Wardak, said there were 119 conflict-related incidents targeting medical facilities and personnel last year, quoting a figure from the United Nations Mission in Afghanistan.

It said 95 of these were attributed to anti-government forces, including the Taliban and Islamic State, with 23 attributed to Afghan security forces, and urged all sides to stop targeted attacks on health care.

As fighting has spread, facilties in heavily contested provinces like Helmand or Kunduz have sometimes been overwhelmed by people seeking treatment, while at others they have been empty because access is blocked by fighting or by checkpoints.

Medical staff have also faced intimidation and threats.

With many clinics run by international aid organizations based in areas outside government control, long negotiations were necessary with insurgent groups and local elders to ensure they could stay open.

"But despite the negotiations, some medical facilities have been closed for days, weeks, or months due to either occupation, or an order issued by armed opposition groups," it said.

With government forces in control of less than 60 percent of Afghanistan, according to the latest U.S. estimates, the report underlines the growing problems in providing adequate health care to the population outside large cities.

The report said the problems were particularly severe for more than 1.4 million internally displaced people in Afghanistan, many living in camps and temporary settlements with only infrequent visits from mobile clinics.

As conflict has escalated since the end-2014 withdrawal of most international troops, the numbers of those in need of health and humanitarian assistance has grown, with malnutrition among children up 40 percent and war injuries up 20 percent.